Monitoring system for forging presses



April 29, 1969 z rru ET AL MONITORING SYSTEM FOR FQRGING PRESSES Sheet orcs INVEN TOR-S ALEXANDER ZEITLIN NATHA M. KRA AROW I BY 261 m w- W his ATTORNEYS April 29, 1969 A. ZEITLIN ET'AL 3,440,348

MONITORING SYSTEM FOR FORGING PRESSES Filed-June l, 1966 Sheet 5 of 5 MOTOR I N VENTORS ALEXANDER ZEITLIN NATHAN M. KRAMAROW To 50 of BfZZ W FZaz Gnu/44.1w mm his ATTORNEYS April 29, 1969 A. ZEITLIN ET MONITORING SYSTEM FOR FORGING PRESSES Sheet of 3 Filed June 1, 1966 FIG. 3

[NYE/VTORS ALEXANDER ZEiTLlN NATHAN M. KRAMAROW BY 5 FLU- mums-0W his ATTORNEYS United States Patent m 3,440,848 MONITORING SYSTEM FOR FORGING PRESSES Alexander Zeitlin, 18 Macy Ave., White Plains, N.Y. 10604, and Nathan M. Kramarow, 147-10 41st Ave., Flushing, N.Y. 11355 Filed June 1, 1966, Ser. No. 554,559 Int. Cl. B21c 51/00 US. CI. 72-31 17 Claims ABSTRACT OF THE DISCLOSURE (e.g. pressing force) to thereby permit authentication of the indicated value of that parameter.

The present invention relates to a new and improved monitoring system for forging presses.

Forging is generally characterized by hammering or pressing of a metallic workpiece into a desired shape. In most instances, the metal is heated to a desired forging temperature; however, a workpiece may also be coldforged.

As a general proposition, the low and medium and carbon steels are usually more readily forged, whereas the alloy steels and high carbon steels are more diflicult to forge and require more attention in the forging process. Moreover, often different forging techniques have to be employed depending upon the different metallurgical properties of the metals and alloys.

In recent years there have been numerous advances in the metallurgical arts which have provided an increasing variety of metals and alloys which can be forged successfully.

It is an object of this invention to provide a monitoring system for forging presses which will determine the following important operating conditions of the press and metallurgical properties of the workpiece: the press speed, the rate of deformation of the workpiece, the pressing force, and the total work required to successfully complete the forging.

More specifically, in one embodiment of the invention, which may be employed with hydraulic presses, the pressing force is derived as a function of pressure of the hydraulic system; the rate of deformation is derived as a product of the speed of the ram and the pressing force; and the total work expended during the work cycle is derived by computer means which integrate the deformation rate with respect to time.

In another version of the invention which may be applied with presses which employ a flywheel system for driving a ram through the work cycle, the total work expended in forming the workpiece is calculated by measuring the difference during a pressing cycle between the maximum kinetic energy level of the driving flywheel when coupled to the ram and the minimum kinetic energy level of the flywheel when so coupled.

In another modified version of the invention applicable with presses employing a flywheel as a source of forming energy, the pressing force may be determined as follows: the speed of the ram is ascertained and then multiplied by conversion factors to determine the tangential force exerted by the flywheel. The tangential force of the flywheel is a function of the press force and by being Patented Apr. 29, 1969 multiplied by a conversion factor may be readily converted into the pressing force.

For a more complete understanding of the present invention reference may be had to a detailed description which follows and to the accompanying drawings, in which:

FIGURE l is a diagrammatic illustration of a hydraulic forging press and a monitoring system for determining important operating conditions of the forging press;

FIGURE 2 is a diagrammatic illustration of another version of monitoring system embodying the present invention;

FIGURE 3 is a schematic diagram of a modification of and addition to the monitoring system of FIG. 2; and 7 FIGURE 4 shows still another modification of and addition to the monitoring system of FIG. 2.

Turning first to a consideration of the schematic illustration of the hydraulic press of FIGURE 1, it is shown to include an upper crosshead member 10, which is fixedly secured to support columns 11 of the press; a movable platen member 12 guided for vertical movement by the columns 11 and carrying an upper impression die 13; and a fixed bed 14 upon which is secured a lower impression die 15.

Operatively associated with the platen 12 is a hydraulic system which includes a main hydraulic cylinder 16 secured in the crosshead 10 and a movable hydraulic ram member 18 arranged to drive the platen 12. During the work cycle of the stroke of the ram 18, the impression dies 13 and 15 engage'a workpiece and squeeze or press it into a desired shape.

The reciprocal stroke of the ram 18 starts at a position where the upper die 13 is disengaged from the workpiece and then the die 13 moves downwardly until it engages the workpiece and continues downwardly forming the workpiece into some desired configuration. Thereafter the die 13 reciprocates upwardly to a disengaged position from the workpiece. The work portion of the stroke will be understood to be that portion of the stroke of the ram 18 when both the dies 13 and 15 are in engagement with the workpiece during the downward movement of the upper die 13.

It will be appreciated that the hydraulic circuit of the press may take many variations; so that for example, it may be designed so that the ram 18 has a fast speed for traveling when die 13 is not yet engaged with the workpiece and a slow speed during the work portion of the stroke. Hydraulic presses are advantageous because their control is quite flexible and permit ready adjustment of both the stroke and pressing force.

Before considering the monitoring system of FIG- URE 1, it may be helpful to briefly outline some of the calculations that it performs in computing various operating conditions of the press.

The rate of deformation of the press will be calculated, at any given time, as being equal to the product of the pressing force times the speed of the upper die 13. The total work involved in the forming process may be calculated by integrating the deformation rate with respect to time.

The monitoring system of FIGURE 1 will now be considered. In order to measure the velocity of the upper die 13, the system is provided with a belt or cable 19, which at one end is fixed to the movable platen 12 whereas at its opposite end it is wound about a rotatably mounted drum 20. During a stroke cycle when the ram 18 moves upwardly or downwardly, the drum 10 will rotate its shaft 21, which provides an input signal to a signal generator 22. The generator 22, in turn, develops a signal representative of the velocity of the upper die 13 and delivers it to a shaft positioning and recording device 25.

Anoutput shaft 26 of the device 25 positions a contact 28 of a logarithmically wound potentiometer 30, the output of which yields a signal representative of the logarithm of the speed of the die 13, as measured in some convenient units such as inches per second.

As will be understood, the device 25 may be embodied by any number of commercially available shaft positioning control arrangements, which are adapted to accurately position an output shaft in response to an input signal. Also, the device 25 includes the necessary equipment for producing a permanent record of the velocity of the die 13 during the work cycle.

Serially connected with the output of the potentiometer 30 is the output of a potentiometer 32, which develops a signal indicative of the logarithm of the pressing force. These two logarithmical signals are each provided as an input to a shaft positioning and recording device 38, which may include a summing amplifier for adding both logarithmical signals, adapted to rotate its output shaft 39 to correspond to the sum of the two signals from the potentiometers 30 and 32. Moreover, the shaft 39 positions a contact 40 of an anti-logarithmically wound potentiometer 41, the output of which is representative of the linear product of the speed of the die 13 and the pressing force, or in other words, the rate of deformation of the workpiece. The deformation signal is used as a speed control signal for an electric motor 50, which is continuously driven and of a conventional design so that its rpm. is a function of the deformation rate of the workpiece.

Briefly returning to the potentiometer 32, it is controlled by an input shaft 51, driven by means of a shaft positioning and recording device 54, which receives a pressure signal input from a bleed line 56 in direct communication with the hydraulic cylinder 16. By a conversion factor, the device 54 transforms the pressure in line 56 into a direct indication of the pressing force exerted by the dies 13 and upon the workpiece. The device 54 will also be understood to include the equipment necessary to provide a permanent record of its output, the pressing force.

It will also be noted that a DC. voltage source 57 is provided for all the potentiometers in the monitoring system, which is preferable over an AC. voltage source arrangement, inasmuch as it will not be subject to noise interference to the same extent as would an AC. voltage system.

In order to integrate the deformation rate signal developed as an ouiput signal of the potentiometer 41 to find the work expended during the entire forming cycle, the output shaft 62 of the motor 50 drives a mechanical counter mechanism 63 which accumulates the total number of revolutions of the shaft 62 and provides a direct reading of the total work expended per stroke. Counter 63 is automatically reset to zero reading after every stroke by suitable resetting means (not shown).

Alternatively, the shaft 62 may be adapted to drive an endless belt 64 mounted on rotatably mounted rollers 65 and 66. A pen member 68 secured to the belt scribes a chart 70 providing a permanent record of the work expended during each work cycle. During each pressing operation, chart 70 is set into motion to pass at known constant speed transversely of and under pen 68 for at least the working portion of the stroke. Conventional means (not shown) are provided to, after each stroke, uncouple belt 64 from motor, reset pen 68 to the base line of the chart and then recouple the belt to the motor.

It is preferable that motor 50 not rotate at times in beween the working portions of successive pressing cycles. Although the means for accomplishing this are not shown, it may be embodied by a number of different arrangements; one such means would be a device responsive to the position of shaft 51 of the device 54 for open circuiting the power supply to the motor 50, so as to prevent its rotation during such times.

Turning now to mechanical forging presses, those presses, being intermittently loaded, often are provided with flywheels which maintain a more uniform stroke during the work cycle. A representative type of such a press is shown in FIGURE 2 and includes a lower platen 71 fixedly secured to the press frame, a structure having support columns 77-80. The frame is of an integral type design consisting of a single casting or a welded structure or may be of a sectionalized design with individual parts fixedly linked together say by means of appropriate shrink rods.

In addition, the press includes an upper movable paten or bolster 82 guided by means of the columns 77-80 and driven in a reciprocal fashion by means of a conven tional pitman rod 83 rotatably connected at one end to the upper platen 82 and at its other end to an eccentric member 84, fixedly secured to and driven by the crank shaft 85 of the press. The crank shaft 85, in turn, is connected through a selectively engageable clutch 86 to a fly wheel 87 driven by a motor 88. Clutch 86 normally disconnects shaft 86 from rotating flywheel 87 but, intermittently, the clutch is engaged to cause the flywheel to drive shaft 85 to thereby effect a pressing stroke. Furthermore, the press includes an upper blocking die 94 mounted on the upper movable platen 82 and a corresponding lower blocking die 93 mounted on the platen 71 and corresponding upper die and lower finishing dies 95 and 96 respectively.

The monitoring system of FIGURE 2 is arranged to calculate a single signal representative of the average stress of the columns 77-80 and then convert this quantity into the pressing force exerted by the dies upon the workpiece during the work cycle. More specifically, each column, of equal rectilinear cross-sectional area, is provided with four separate strain gages 101-104, which gages measure the elongation of each side of the column. The strain gages of each column provide an input signal to a computing device 108 which includes the necessary control circuitry for developing a single signal indicative of the average strain in each column and then, using each of those four signals, computes a single signal representative of the average strain for all the columns 77-80 taken as a whole.

If necessary, the strain gages should be temperature compensated, and preferably they should be enclosed by a covering adapted to withstand sudden shock loads.

After computing the average strain for all the columns, the computing device 108 derives an output signal representative of the total pressing force of the dies upon the workpiece by multiplying the average strain with the appropriate conversion factor (Hookes law) which depends on the total cross-sectional area of the columns and the modulus of elasticity of the columns.

The reason for providing four strain readings for each column is as follows. During the Work cycle, the dies cooperating to form the workpiece will for the most part transmit axial forces to the columns; however, some lateral forces may be transmitted to the columns 77-80 producing bending stresses in the columns. Consequently, any given cross-section of a column may have portions which are subject to tensile bending stresses and other portions subject to compressive bending stresses. In calculating the average stress in each column, four strain gages are utilized which when their outputs are averaged, provide an indication of the average strain in the columns which then can be used to compute the average stress in the column, which will produce the correct value for the total column force.

Returning now to the device 108, its output signal, representative of the pressing force, is delivered to a shaft positioning and recording unit 114, arranged to accurately position its output shaft 115, which, in turn, positions a contact of a logarithmically wound potentiometer 122. Serially connected with the output of potentiometer 122 is the output signal from a potentiometer 125, which is indicative'of the logarithm of the velocity of the upper dies 94 and 95 during the work cycle. These two logarithmical signals are delivered to a shaft positioning and recording device 38, adapted to develop a signal representativeof the sum of both of these logarithmic signals and to utilize this new signal to control the position of an output shaft and a contact of an antilogarithmically wound potentiometer 41 driven thereby.

The potentiometer 125 includes a contact member which is positioned by means of a shaft 126 driven by the output of a shaft positioning and recording device 128; the position of the shaft 126 of course representing the velocity of the upper dies. An input signal to the device -128 isderived by a signal generator 130 and is representative of the velocity of the upper dies 94 and 95. A cable 134 fis fixed at one end of the movable platen 82 and wound about a rotatably mounted drum 138, driving a shaft 139, which provides the necessary input signal to the signal generator 130. 1 The output of the potentiometer 41, of course, represents the deformation rate of the workpiece during the work cycle. Moreover, the potentiometer 41 performs the identical function as the potentiometer 41 in FIGURE 1. The remaining computational means for providing an indication of the total work expended is the same as those used in FIGURE 1, and so a description of that remaining means rieed not be repeated.

It will be briefly noted that, as with the FIGURE 1 monitoring system, a DC. source of voltage 140 is provided for the various electrical components in the monitoring system of FIGURE 2.

During the working portion of a pressing cycle for flywheel driven presses, energy is removed from the flywheel, and a reduction in speed of the flywheel results. While the press is idling (i.e., clutch 86 is disengaged), this energyis replaced by motor 88 which brings the flywheel backup to speed. The energy delivered by a flywheel is often expressed by the equation:

182.4 g whereinE is the change in energy in foot-pounds, w is weight in pounds, k is radius of gyration in feet, g is the acceleration due to gravity and N and N are respectively the maximum and minimum angular velocity of the flywheel in revolutions per minute.

The above equation can of course be simplified to the equation:

wherein K equals the term (wk 182.4 g.

Another method according to this invention, as illustrated by the monitoring system of FIGURE 3, for determining the work expended during the work cycle is to calculate the quantity K(N N from measurements of N and N made'when the flywheel is coupled to the press.

Just before the'upper die Teaches bottom dead center, the lowest velocity N of the flywhel is reached, whereas the maximum speed (of significance to the measurement) will of course be attained prior to when the workpiece is engaged by the upper die but after the flywheel has been coupled to the press to bring the eccentric 84 up to maximum rotary speed.

Turning now to FIGURE 3, the illustrated press includes many of the same elements as that of FIGURE 2 which are therefore designated with the same numerals.

The basic device for calculating N N is designated by number 153 and may be of a number of designs but, as shown, is a moving coil instrument having two coils 153a and b, with coil 1531; of the device 153 being movable whereas coil 153a is fixed so that the device 153 develops a rotating force which positions an output shaft 160, the angular position of the shaft 160 being proportional to the square of the input signal from the generator 156. As is conventional, instrument 153 includes a spring (not shown) for restoring moving coil 1531) to zero position upon de-energization of the instrument.

A signal developed by the generator 156 is representative of the angular velocity of the flywheel 87. In order to provide this signal, a rotating shaft 155, driven by means of the flywheel 87, is coupled to generator 156 to cause it to produce an output signal.

More specifically, the output of the signal generator 156 is delivered to the device 153 through a reversing switch 164, which moves between three positions, the illustrated neutral position wherein no signal is delivered to the device 153, a left hand position wherein a signal representative of the maximum velocity of the coupled flywheel 142 is delivered to the device 153, and the right hand posi tion wherein the minimum velocity signal is provided as an input to the device 153.

The switch 164 actually includes two contacts which are gang mounted upon the end portion of a shaft 165 normally urged by a spring 166 to a position wherein the contacts are disposed in the neutral position. A coil 167 is wound about an armature (not shown) aflixed to the shaft 160 and centrally disposed in relation to the coil. Coil 167 is adapted to be energized each time a contact 170 mounted on the eccentric 84 completes a circuit with battery 168 by either contact 171 or 173. When the contacts '170 and 173 engage, the coil 167 will exert a force on the shaft moving the switch 164 to the right hand position and a signal indicative of the'minimum speed of the flywheel 87 will be provided as an input to the device 153, whereas when contact 170 engages the contact 171, the switch 164 will be moved to the left and the device 153 will be provided with a signal representative of the highest velocity of the flywheel during the pressing stroke cycle.

As aforesaid, the output of the device 153 is a shaft 160 which, it will be noted, is connected by a clutch to driven shaft 181 adapted to position an indicator device 182. The clutch 180, biased by a tension spring 185 to a normally disengaged position, engages the output shaft 160 to the driven shaft 181 when a coil 186 is energized, which condition indicates a signal is being provided to the device 153. Coil 186 surrounds an armature (not shown) affixed to shaft 160 to be leftward of the center of the coil when the shaft is biased leftward by spring 185.

A brake 192 mounted about the shaft 181 normally is in a braking position preventing the pointer of the device 182 from rotating. However, when a coil 193 is energized, it releases the brake 192, permitting the shaft 160 to position the indicator 182, which occurrence, as is clear from FIGURE 3 takes place whenever the contact 170 engages any of the contacts 171-173. Moreover, it will be understood that the shaft 181 is normally urged by a spring (not shown) to a neutral or zero position so that in the event the brake 192 is released and no signal provided to the device 153, the indicator 182. will return to its zero position. Such a situation takes place when the contact 170 wipes across the contact 172.

The calculating process is as follows. When the contact 170 engages contact 172, the brake 192 is released and inasmuch as, at this time, coil 186 is deenergized and clutch 180 is thereby disengaged to uncouple shaft 181 from shaft 160, the device 182 will be returned to its zero position by the restoring spring for the device.

Later, when the contact 170 engages the contact 171, a circuit is completed to the coil 1 67, which causes the switch 164 to move to its left hand position wherein a signal from the generator 156 is directed to the device 153. At the same time the coil 193 is energized releasing the brake 192 thereby permitting the device 153 to move the indicator 182 in, say, the clockwise direction to a position representative of the quantity N When the contact 170 disengages from the contact 171, the coil 193 is deenergized, locking the brake 192, and thus the indicator 182 will remain in this position. Finally,

when the contacts 170 and 173 engage, a signal will again be impressed upon the device 153. This time, the energized coil 167 will move the switch 164 to its right hand position to cause current flow through device 153 in a direction opposite to that the current took previously. Hence, the shaft 160 will rotate the shaft 181 counterclockwise from its N position in an amount proportional to N The device 182 is now displaced clockwise from its zero position in an amount indicating (N N The device 182 will be understood to include the necessary circuitry for multiplying the quantity (NE-N by the appropriate K factor to determine the work expended during the work cycle.

As previously indicated, the pressing force may be calculated by determining the tangential force exerted by the flywheel during the forming process. More particularly, as the kinetic energy of the flywheel is used up during the pressing stroke cycle, the speed of the flywheel decreases and this may be expressed by the following equation:

wherein F, is the decelerating tangential force, A is the deceleration, and M is equal to the mass of the flywheel.

The relationship between the tangential force F and pressing force P is given by the following equations:

F (sin a|b)P (cos b) cos b Ft sin (a+b) (3) wherein a is the angle between the crankshaft and a vertical plane passing through the center line of the crankshaft and b is the corresponding angle between the vertical plane and the pitman.

The arrangement shown in FIGURE 3 is adapted to solve the above Equation 3 and thereby compute the pressing force. This is accomplished as follows: the output of the signal generator 156 provides an input to a differentiating and computing circuitry network 208, which differentiates the velocity signal to derive the deceleration of the flywheel 87 and thereafter solves Equation 1 providing an input to a shaft positioning and recording device 209 representative of the tangential force F, of the flywheel 142. In response to this input signal, the device 209 positions an output shaft 210 which moves a contact of a logarithmically wound potentiometer 211, adapted to develop an output representative of the logarithm of the tangential force F Also responsive to the output of the signal generator 156 is a shaft positioning and recording device 215 which positions its shaft 216 and moves a contact of a logarithmically wound potentiometer 217, in turn providing an output singal representative of the logarithm of the angular velocity (v) of the flywheel 142.

A recording device 222 is responsive to both the outputs of the potentiometers 211 and 217, and consequently provides an output signal which represents the sum of two logarithms or the product v F on a logarithmic scale. This product may be plotted and considered as the rate of deformation of the workpiece.

In order to calculate the pressing force P, in accordance with Equation 3, a logarithmically wound potentiometer 224, driven by means of a shaft 225 connected to the main crankshaft 84, is adapted to provide an output which represents the following term (cos b)/sin (a-l-b) The output of both the potentiometers of 211 and 224 are serially connected and provide inputs into a device 230 which provides an indication, in a logarithmic fashion of the pressing force P.

There are two indeterminate points in the solution of Equation 3 inasmuch as the sin (a-i-b) will be zero in the position when the ram is at lower dead center and at its topmost position. Of course, only the lower dead center position need be considered as the top dead center position is reached while the press is doing no work. Nevertheless, the device 230 will develop proper values relatively close to lower dead center to provide a sufl'lcient basis for interpolation to approximately determine the pressing force at the lower dead center position.

Another variation of the above arrangement is shown in FIGURE 4. Here a movable platen 240 includes a contact 246 which is positionable along a linear potentiometer 247, wound so as to provide an output representation of the term (sin a+b)/cos b The potentiometer 247 provides an input to a shaft positioning and recording device 250 which positions an output shaft 251 adapted to move the contact on a logarithmically Wound potentiometer 254.

A device 114 (the same as the device 114 of FIGURE 2) is arranged to provide an output by means of its shaft 115' representative of the pressing force. The shaft 115' positions a movable contact on the logarithmically wound potentiometer 260. Both the potentiometers 250 and 260 provide input signals to a device 261 which provides an output representing on a logarithmic scale the tangential force F solving Equation 2, without anyindeterminate conditions. The solution may, if desired, be used to check the value of the tangential force calculated by a circuit of the FIGURE 3 configuration. It should also be noted that the potentiometer 247 could be wound to represent the logarithm of the conversion factor of Equation 2 such that tap 246 can be substituted for the tap of'element 254 to thereby permit elimination of all of elements 250, 251 and 254.

In connection with the foregoing, it'is to be understood that FIGS. 2, 3 and 4 show respective systems which are usable either independently of each other or conjointly with each other to form an overall system. In that overall system, indications are derived in two different ways of each of the parameters of pressing force, rate of deformation, flywheel tangential force and Work expended, wherefore the two indications of each of these parameters may be checked against each other for the purpose of authenticating those indications. That is, the readings of devices 114 (FIG. 2) and 230 (FIG. 3) may be compared to authenticate the pressing force indication, those of device 38 and of device 222 (FIG. 3) may be compared to authenticate the indication of rate of deformation, the readings of device 209 (FIG. 3) and device 261 (FIG. 4) may be compared to authenticate the indication of F and those of device 63 (shown in FIG. 1 but part of the FIG. 2 system) and of device 182 (FIG. 3) may be compared to authenticate the indication of work expended per pressing cycle. If the two indications of any parameter do not substantially agree, both indications are, of course, rejected and the system is inspected to determine which indication is in error and is then repaired to correct that error.

Although the invention has been described herein with reference to a specific embodiment, many modifications and variations therein will readily occur to those skilled in the art. Thus, for example, while the systems disclosed herein employ simple electromechanical elements to effect the computations and indications involved in the present invention, purely electronic components (including solid state components) may be used in place of one or ones of those electromechanical elements to perform equivalent functions. Accordingly, all such variations and modifications are included within the intended scope of the invention as defined by the following claims.

We claim:

1. A monitoring system for forging presses having a fixedly mounted die and a movable die mounted upon a ram member which carries the latter die through a pressing cycle, the monitoring system comprising press force measuring means for measuring an operating condition of the press during the pressing cycle and generating a signal representative of the pressing force in response thereto, speed measuring means for deriving a signal which is indicative of the velocity of the upper die during the pressing cycle, and computer means responsive to the pressing force signal and the speed signal for developing a signal indicative of the deformation rate of the workpiece.

2. A monitoring system as set forth in claim 1 wherein the computer means includes means for integrating the deformation rate signal with respect to time to generate a signal which represents the work expended during the pressing cycle.

3. A monitoring system as set forth in claim 1 wherein the forging press is of a variety including a system for hydraulically actuating the ram and the pressing force measuring means including means for monitoring the pressure in the hydraulic system to derive, a pressure signal and means responsive to the pressure signal for developing a signal which represents the pressing force generated by the dies engaging the workpiece.

4. A monitoring system as set forth in claim 3 wherein the computer means includes means for integrating the deformation rate signal with respect to time to generate a signal which represents the work expended during the pressing cycle.

5. A monitoring system as set forth in claim 1 wherein the forging press includes a flywheel which drives the ram through the pressing cycle, the press force measuring means comprising means responsive to the speed of the flywheel for deriving a signal representative of the tangential force exerted by the flywheel during the pressing cycle, and means responsive to thetangential force signal for providing a signal which represents the'pressing force.

6. A monitoring system as set forth in claim 5 wherein the computer means includes means for integrating the deformation rate signal with respect to time to generate a signal which represents the work expend-ed during the pressing cycle.

7. A monitoring system as set forth in claim 1 wherein the press force measuring means comprises means measuring variations in the press frame for developing a signal indicative of the average strain in the frame of the press, and means responsive to the average strain signal for deriving a signal representative of the pressing force.

8. A monitoring system as set forth in claim 7 wherein the computer means includes means for integrating the deformation rate signal with respect to time to generate a signal which represents the work expended during the pressing cycle.

9. 'A monitoring system for forging presses including a fixed die, a movable die mounted upon a ram member and a flywheel which drives the die through the pressing cycle, the monitoring system comprising means for deriving a first energy signal representative of the maximum kinetic energy of the press before the beginning of the work portion of the pressing cycle, and means for deriving a second energy signal representative of the minimum kinetic energy of the press during said working portion, and means responsive to the difference between said energy signals for producing a signal which is a function of the total work expended forming the workpiece durin g the work cycle.

10. A monitoring system for forging presses having a first fixed die and a second movable die mounted upon a ram member which is driven by means of a flywheel during the pressing cycle, the monitoring system including means for deriving a signal representative of the speed of the movable die, means responsive to the die speed signal for providing a signal representative of the tangential force exerted by the flywheel during the press-ing cycle, and means responsive to the tangential force signal for producing a signal which is representative of the pressing force.

11. A monitoring system according to claim 10 including computer means responsive to the pressing force signal and the speed signal for generating a signal representative of the work expended during the pressing cycle.

12. A monitoring system as in claim 11 including computer means for calculating the deformation rate of the workpiece during the pressing cycle.

13. A monitoring system for a forging press having a guide frame, a fixed lower die fixedly secured to the frame, and an upper die which is mounted on a ram movable through the pressing cycle, the monitoring system comprising stress gage means for measuring variations in the frame to develop a signal which represents the average stress in the frame during the pressing cycle, and means responsive to the average stress signal for deriving a signal representative of the pressing force during the pressing cycle.

14. A monitoring system as in claim 13 including means for producing a signal representative of the speed of the upper die and computer means responsive to both the speed and pressing force signals for deriving a signal representative of the deformation rate of the workpiece.

15. A monitoring system as in claim '14 including means for integrating the deformation rate signal with respect to time to generate a signal representative of the work expended during the pressing cycle.

16. -A monitoring system for forging presses including a fixed die, a movable die mounted upon a ram member and a flywheel which drives the die through the pressing cycle, the monitoring system comprising signal storage means, first signal means actuated before the working portion of the pressing cycle for deriving a first signal representative of the maximum kinetic energy of the flywheel when coupled to said ram member and providing said signal as an input to the signal storage means, second signal means for producing a second signal representative of the minimum kinetic energy of the flywheel and providing the latter signal as an input to the signal storage means, the signal storage means being adapted to subtract the second signal from the first and yield a signal which is a function of the Work expended during the pressing cycle.

17. A monitoring system for a forging press comprising, first force measuring means responsive to the pressing force exerted by said press during a pressing cycle to provide by a first mode of signal derivation from said force a first determinate signal of said force, second force measuring means responsive to said same pressing force to provide by a second mode of signal derivation from said force which is independent of said first mode a second determinate signal of said force, and first and second indicating means responsive to, respectively, said first and second signals to provide separate determinate indications of said pressing force as measured by said first mode and second mode so as to permit authentication of the value of said force by checking said indications against each other.

References Cited UNITED STATES PATENTS CHARLES w. LANHAM, Primary Examiner.

G. P. CROSBY, Assistant Examiner.

US. Cl. X.R. 

